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                                                                    Exhibit 4.1A


                   AMENDMENT TO AND SUPPLEMENTAL INDENTURE


                  THIS AMENDMENT is made this 23rd day of May, 1995, by and
among Chattem, Inc., a Tennessee corporation (the "Company"), Signal Investment
& Management Co., a Delaware corporation (the "Guarantor") and SouthTrust Bank
of Alabama, National Association, a national banking association (the
"Trustee"), under the following circumstances:

                  A.       The Company has issued its Series B Senior
Subordinated Notes due 2004 in the aggregate principal amount of $75,000,000
(herein the "Notes").

                  B.       The Notes are secured by the Indenture dated
August 3, 1994 among the Company, the Guarantor and the Trustee ("Indenture").

                  C.       The Company and the Guarantor, having received the
written approval of the holders of at least a majority in interest in
principal amount of the Notes pursuant to Section 9.02 of the Indenture, and
the Trustee desire to amend the Indenture in order to amend the definition of
Permitted Investment as provided hereinafter.

                  NOW, THEREFORE, in consideration of the premises and of the
mutual covenants and agreements contained in this Agreement, the parties agree:

                  1.       The definition of "Permitted Investment" as set
forth in Section 1.01 of the Indenture shall be deleted in its entirety and
in lieu thereof shall be inserted the following:

                           "Permitted Investments" means (i) any Investments in
                  the Company or in a Wholly Owned Subsidiary of the Company
                  that is a Guarantor; (ii) any Investments in Cash Equivalents;
                  (iii) Investments by the Company or any Subsidiary of the
                  Company in a Person, if as a result of such Investment (a)
                  such Person becomes a Wholly Owned Subsidiary of the Company
                  and a Guarantor or (b) such Person is merged, consolidated or
                  amalgamated with or into, or transfers or conveys
                  substantially all of its assets to, or is liquidated into, the
                  Company or a Wholly Owned Subsidiary of the Company that is a
                  Guarantor; (iv) any investment that would be a Cash Equivalent
                  but for its maturity being greater than six months, provided
                  such maturity is not greater than one year; (v) Investments
                  consisting

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                  of consideration received by the Company or a Wholly Owned
                  Subsidiary of the Company that is a Guarantor in an Asset
                  Sale which consideration is not and is not required to be
                  in the form of cash or Cash Equivalents pursuant to Section
                  4.10 hereof; and (vi) shares of capital stock, notes,
                  warrants or other securities received by the Company or a
                  Wholly Owned Subsidiary that is a Guarantor in partial or
                  total satisfaction of obligations created in the ordinary
                  course of business pursuant to a plan of reorganization,
                  liquidation, restructuring, decree or order by a court
                  having jurisdiction under the Federal bankruptcy laws, as
                  now or hereafter constituted, or under any other applicable
                  Federal or state bankruptcy, insolvency, receivership or
                  other similar laws or pursuant to an assignment for the
                  benefit of creditors or voluntary settlement or
                  restructuring.

                  2.       Except as expressly set forth herein, this
Amendment to the Indenture shall not supersede or otherwise modify the terms
and conditions of the Indenture.

                  IN WITNESS WHEREOF, this Amendment to the Indenture has been
executed by a duly authorized officer of the Company, the Guarantor and the
Trustee.



Dated as of May 23, 1995.

ATTEST:                                         CHATTEM, INC.


By:                                    By:
   ------------------------------------   --------------------------------
   Secretary                                       Robert E. Bosworth,
                                                   Executive Vice President
[CORPORATE SEAL]



Dated as of May 23, 1995.


ATTEST:                                         SIGNAL INVESTMENT & MANAGEMENT
                                                CO., a Guarantor

By:                                    By:
   ------------------------------------   --------------------------------
   Secretary                                       Robert E. Bosworth,,
                                                   President
[CORPORATE SEAL]


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Dated as of May 23, 1995.


ATTEST:                                         SOUTHTRUST BANK OF ALABAMA,
                                                NATIONAL ASSOCIATION

By:                                    By:
   ------------------------------------   --------------------------------
                                                   Name:
                                                   Title:
[CORPORATE SEAL]